Carry-over and stopping switches with improved arcuate
shaped contact structure



S p 1967 w. J. SCHAAD ETAL 3,344,242

CARRY-OVER AND STOPPING SWITCHES WITH IMPROVED ARCUATE SHAPED CONTACT STRUCTURE Filed Oct. 4, 1965 a Sheets-Sheet 1 william J .Schaad ZUilIz'am 7?..5c1zink IN VENTORS Sept. 26, 1967 w. SCHAAD ETAL 3,344,242

CARRY-OVER AND STO NG SWITCHES WITH IMPROVED ARCUAT SHAPED CONTACT STRUCTURE Filed Oct. 4, 1965 T 5 Sheets-Sheet 5 HQG 2% w I] m 4 lwfwo/zs William .1 5011010101 20171121212 VZSchink @WM M Y diys United States Patent Ofilice Patented Sept. 26, 1967 3 344 242 CARRY-OVER AND STOFPING SWITCHES WITH IIVIPROVED ARCUATE SHAPED CONTACT 15 Claims. (Cl. 200-11) This invention relates to electrical switches.

One object of the present invention is to provide a new and improved switch which will find various applications and uses, but which is especially well suited for use as a carry-over and stopping switch in connection with an electric motor for indexing the control shaft of a television tune-r, or any other similar control member.

A further object is to provide a switch of the foregoing character having a new and improved construction utilizing a movable contactor which bridges across a plurality of stationary contact points.

Another object is to provide such a switch having a new and improved construction whereby the switch operates freely and with very little friction so that the switch may be returned to neutral by a very small spring effort.

A further object is to provide such a new and improved switch in which the movable operating member of the switch is formed in a new and improved manner with an operating arm and a pair of spring engaging arms for engagement with and operation by external return springs.

Another object is to provide a switch of the foregoing character having a new and improved construction including a movable contactor which is carried by a movable operating member and is adapted to be tilted by one or more cams on the operating member, whereby the switch will operate freely and with a minimum of friction.

Another object is to provide such a new and improved switch which is extremely economical, yet is unusually serviceable and durable.

Further objects and advantages of the present invention will appear from the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a front elevational view of a carry over and stopping switch to be described as an illustrative embodiment of the present invention, the switch being illustrated is applied to the control of an electric motor drive for a television tuner.

FIG. 2 is an enlarged fragmentary elevation similar to FIG. 1 but showing the switch in its carry-over position, rather than in its neutral position, as in FIG. 1.

FIG. 3 is a fragmentary vertical section taken generally along the line 3-3 in FIG. 1.

FIG. 3a is an enlarged fragmentary section taken through the contactor and corresponding to the lower portion of FIG. 3.

FIG. 4 is a fragmentary enlarged section taken through the contactor of the switch, generally along the line 44 in FIG. 3.

FIG. 5 is a front elevational view of a modified switch,

which is similar to that shown in FIG. 1 but is intended for use with a unidirectional motor, rather than a reversible motor.

FIG. 6 is a side elevational view of the switch FIG. 5.

FIG. 7 is a top view of the switch of FIG. 5.

FIG. 8 is a rear view of the switch of FIG. 5.

FIG. 9 is a schematic circuit diagram showing a typical application for the switch of FIGS. 1-4.

FIG. 10 is a schematic circuit diagram showing a typical application of the switch of FIGS. -8.

As already indicated, FIG. 1 illustrates a carry-over and stopping switch as applied to the motor drive for a television tuner 12. It will be seen that the tuner 12 has a channel selector shaft 14 which may be turned to a series of positions corresponding to the television channels covered by the tuner 12. In the illustrated construction, the shaft 14 may be indexed to thirteen different positions, corresponding to the twelve channels currently allocated for Very High Frequency (VHF) television, plus an extra position to switch over to Ultra High Frequency (UHF) reception. An electric motor 16 is provided to index the channel selector shaft 14.

In the illustrated drive, the electric motor 16 has a shaft 18 which is formed with a pinion 20, adapted to mesh with a gear 22. Another gear or pinion 24 of smaller size is formed integrally with the gear 22. The gear 24 meshes with a larger gear 26. A disc 28 is secured to the gear 26 and is fitted with a camming pin 30. As shown to advantage in FIGS. 1 and 2, the pin 30 is adapted to mesh with a star wheel 32 which is secured to the channel select-or shaft 14. The star wheel 32 is formed with a series of radial slots 34 for receiving the pin 30. Cam lobes or arms 36 are formed on the star wheel 32 between the slots 34. With this construction, the star wheel 32 is indexed through one step for each complete revolt.- tion of the disc 28. Each step corresponds to the angle between the adjacent slots 34. The television tuner 12 may include a detent mechanism, not shown, for detaining the channel selector shaft 14 in each of its thirteen positions.

The general purpose of the switch 10 is to stop the electric motor 16 When the shaft 14 has been indexed to each of the desired channel settings. The arrangement is such that the switch 10 causes the motor 16 to carryover and continue running as the channel selector shaft 14 passes various channel settings which are not desired.

The illustrated switch 10 comprises a frame or base plate 40 which in this case is made of electrically insulating material. It is preferred to employ a material which is highly resistant to electric arcing such as a melamine coated phenolic laminate. Such materials will resist being carbonized by the electric arcing which occurs during the operation of the switch. A centrally disposed contact point 41 and two other contact points 42 and 43 are mounted on the base plate 40, as shown to advantage in FIGS. 2 and 4. As illustrated, the central contact point 41 is frusto-conical in shape, while the contact points 42 and 43 are spherically curved or dome-shaped. The contact points 41, 42 and 43 may be in the form of heads of rivets 46, 47 and 48. Preferably, the contact points 42 and 43 are made of a silver contact alloy and are welded or otherwise secured to the rivets 47 and 48, which may be made of copper or the like. The central contact point 41 may be made of copper or a copper alloy and may be formed integrally with the rivet 46. Preferably, the contact points 41, 42 and 43 are of considerable height so as to project well beyond the front surface of the insulating base plate 40, so that the effect of electrical arcing on the base plate will be minimized. Terminals 51, 52 and 53 are secured to the base plate 40 by the rivets 46, 47 and 48. Additional rivets 56, 57 and 58 may also be employed to secure the terminals 51, 52 and 53 to the base plate 40. The terminals 5153 are adapted to receive suitable spring connectors. In addition, the terminals 51, 52 and 53 are provided with side lugs 51a, 52a and 53a to which wires may be soldered. It will be understood that wires may also be soldered to the terminals 51-53, if desired.

The switch 10 also comprises a movable operating member or carriage 60 which is supported for swinging movement by a pivot pin 62 secured to the base plate 40. The operating member 60 may be made of electrically insulating material, which should also be highly resistant to heat and electric arcing.

A movable cont actor 64 is carried by the operating member 60. When the operating member 60 is in its neutral position, as shown in FIG. 1, the contactor 64 engages only the central contact point 41. When the operating member 60 is swung to one of its operating positions, as shown in FIG. 2, the contactor 64 engages the contact points 41 and 42 and forms a conductive bridge therebetween. The operating member 60 may be swung in the opposite direction to its other operating position, in which the contactor 64 engages the contact points 41 and 43, so as to form a conductive bridge therebetween. Further advantageous features of the contactor 64 will be described presently.

The illustrated operating member 60 is provided with an arm 66 having a generally triangular tip portion 68 adapted to be operated by the drive disc 28. It will be seen that the drive disc 28 is formed with a sector-shaped notch 70 for receiving the triangular tip portion 68. The ends of the notch 70 are in the form of shoulders 71 and 72 adapted to engage and operate the triangular tip 68 of the arm 66. When the disc 28 is rotated counterclockwise, the shoulder 71 engages the triangular tip 68 and causes the arm 66 to swing in a clockwise direction, to the position shown in FIG. 2. The circular periphery 74 of the disc 28 engages the triangular tip 68 and retains the arm 66 in this position. It will be seen that the contactor 64 engages the contact points 41 and 42 in this position of the switch. The closure of the circuit between the contact points 41 and 42 causes the motor 16 to continue running so that the indexing movement of the channel selector shaft 14 will be completed, as will be described in greater detail presently.

For any particular tuner, it will not be desirable to stop at every channel setting, because various television channels will be unused. For this reason, the illustrated tuner 12 is arranged so that the operation of the switch will be maintained as the channel selector shaft 14 is indexed past the undesired channel settings.

Thus, each of the arms or teeth 36 of the star wheel 32 is provided with an adjustable cam lobe 76 which may be turned manually between its active position, extending radially, and its inactive position, at right angles to a radial direction. In FIGS. 1 and 2, some of the cam lobes 76 are in their active positions, while others are in their inactive positions. The variou lobes 76 correspond to the television channel settings.

The cam lobes 76 control the return springs 78 and 80 for the switch 10. It will be seen that the return springs 78 and 80 are mounted on a cam follower 82 which is adapted to be operated by the cam lobes 76. The cam follower 82 is mounted for a combination of sliding and rocking movement. Thus, the cam follower 82 is provided with a pair of arms 88 and 90 which are formed with curved slots 92 and 94. Stationary studs or posts 96 and 98 are slidably received in the slots 92 and 94. The posts 96 and 98 also serve as supports for the base plate 40 of the switch. Thus, screws 100 and 102 are employed to secure the base plate 40 to the posts 96 and 98.

The return springs 78 and 80 are in the form of spring leaves or fingers which are engageable with arms 104 and 106 on the operating arm 60 of the switch 10. The arms 104 and 106 are on opposite sides of the central operating arm 66.

FIG. 1 shows the switch 10 in its neutral position. The channel selector shaft 14 is in one of its desired channel settings, and the cam follower 82 is engaged by one of the adjustable cam lobes 76. It will be seen that the cam follower 82 is held downwardly by the cam lobe 76, so that the return springs 78 and 80 engage the arms 104 and 106 on the movable member 66 of the switch 10. Thus, the springs 78 and 80 are effective to center the movable member in its neutral position, with the contactor 64 engaging only the contact point 41. The disc 28 is oriented so that the triangular point or tip 68 of the arm 66 is received in the notch 70.

When it is desired to change to another channel, the

motor 16 is energized. This causes rotation of the disc 28.- It will be assumed that the disc 28 is rotated counterclockwise. The shoulder 71 engages the arm 66 and swings it clockwise, to the position shown in FIG. 2. Thus, the carriage 60 is moved to one of its operating positions, in which the contactor 64 engages the contact points 41 and 42. The closure of the circuit between the I contact points 41 and 42 causes the motor to continue running. This action may be brought about by a circuit of the type shown in FIG. 9, as will be described in greater detail shortly.

The movement of the carriage 60 in a clockwise direction, to the position shown in FIG. 2, causes flexure of the left-hand return spring 78, due to the force exerted on the spring by the arm 104. The rotation of the disc 28 causes the pin 30 to move the star wheel 32 through one step. Thus, the cam lobe 76 which was formerly in engagement with the cam follower 82 is moved away, and the next cam lobe 76 is moved opposite the cam follower. If the next cam lobe 76 is in its inactive position, as in the case of the cam lobe 76 which is opposite the cam follower 82 in FIG. 2, the pressure on the cam follower 82 is released, whereupon the return spring 7 8 causes the cam follower to rock upwardly in a clockwise direction to the position shown in FIG. 2. In this position, the return spring 78 no longer exerts pressure on the arm 104. Thus, when the notch 70 in the disc 28 passes the triangular openati-ng arm 66, the operating arm remains in its operated position, because of the lack of a return spring action. The motor continues to run while the disc 28 rotates through another revolution. This carry-over action occurs whenever an inactively positioned cam lobe 76 comes opposite the cam follower 82.

When an actively positioned cam lobe 76 comes opposite the cam follower 82, the cam lobe pushes the cam follower 82 downwardly, so that the return spring 78 is again flexed. Thus, the return spring 78 exerts pressure on the arm 104 of the switch. When the notch 70 comes opposite the operating arm 66, the return spring 78 immediately returns the operating arm 66 and the switch carriage 60 to its neutral position. Thus, the motor circuit is broken, with the result that the motor stops running. Accordingly, the television tuner comes to rest at this channel setting.

As already indicated, FIG. 9 shows a typical operating circuit for the motor 16. In this case, the motor 16 is of the reversible type and is provided with three leads 111, 112 and 113. For one direction of operation, voltage is applied between the leads 111 and 112. The leads 111 and 113 are used for the reverse direction of operation.

In the circuit of FIG. 9, the lead 111 is connected directly to one side of a source of electrical power, represented by power line wires 114 and 116. A switch 118 is provided to start the motor 16. As shown, the switch 118 comprises a contactor 121 which is movable between contacts 122 and 123. The power line wire 116 is connected to the contactor 121, while the motor leads 112 and 113 are connected to the contacts 122 and 123. The contactor 121 may be operated either manually or by a suitable relay. When the contactor 121 is moved against the contact 122, the motor 16 operates in one direction. The reverse direction of operation is obtained when the contactor 121 is moved against the contact 123.

The carry over switch 10 is effectively connected in parallel with the starting switch 118. Thus, the contact point 41 is connected to the power line wire 116, while the contact points 42 and 43 are connected to the motor leads 112 and 113. Due to the provision of the carryover switch 10, momentary operation of the starting switch 118 is sufiicient to cause the motor to operate through a complete cycle. The rotation of the motor 16 operates the carry-over switch 10, so that the motor continues to operate until the television tuner has been indexed to the next desired channel setting.

-It will now be desirable to return to the contactor 64 for a more detailed description. As shown to best advantage in FIG. 4, the contactor 64 comprises a disc which is engageable with the contact points 41, 42 and 43. The disc-shaped contactor 64 projects rearwardly from the movable carriage 60 of the switch and is partly received within a bore 126 formed in the carriage. The contactor 64 is formed with a guide stem or start 128 which projects forwardly from the contactor along the axis of the bore 126 and is loosely received in an opening 130. It will be seen that the opening 130 is formed in the front portion of the carriage 60 so as to communicate with the bore 126.

The disc-shaped contactor 64 is biased rearwardly against the contact points 41-43 by a spring 132, which in this case is in the form of a cone-shaped coil spring received around the stem 128 and compressed between the contactor 64 and a shoulder 134 within the carriage 6. It will be seen that the shoulder 134 is formed between the opening 130 and a reduced portion 136 of the bore 126. The front end portion of the Spring 132 is received and centered within the reduced portion 136 of the bore 126.

The disc-shaped contactor 64 is formed with a marginal ridge 138 which is annular in form. Generally, the annular ridge 138 is, curved in cross section, but it has a frusto-conical inner slope 138a. The contactor 64 has a central portion .139 which is recessed relative to the rearwardly projecting ridge 138.

To improve the operation of the switch 10, the opening 130 for the stem 128 is formed with a pair of slanting cam surfaces 141 and 142. When the switch carriage 60 is in its central or neutral position, both of the cam surfaces 141 and 142 engage the stem 128 and have the eifect of centering it and maintaining it in a level position so that the proper clearances will be maintained between the contaotor and the contact points 42 and 43. The radial distance between the axis of the contactor 64 and the axis of the pivot 62 is less than the radial distance between the axis of the pivot and the axis of the contact point 41. Thus, the axis of the contactor 64 is at a higher level than the axis of the contact point 41 when the carriage 60 is in its neutral position. As shown in FIGS. 3 and 3a, the frusto-conical contact point 41 engages the lower portion of the frusto-conical inner slope 138a of the ridge 138 on the contactor 64. Such engagement between the contactor and the central contact point 41 tends to center and locate the carriage 60 in its central or neutral position. This centering action is supplemented by the centering elTect of the cam surfaces 141 and 142. When the carriage 60 is swung clockwise, as shown in FIG. 2, the curved ridge 138 engages'and slides onto the contact point 42. The radial distance between each of the contact points 42 and 43 and the pivot 62 is substantially less than theradial distance between the pivot and the central contact point 41. Thus, only the curved portion of the ridge 138 is engageable with the contact points 42 and 43. The movement of the carriage 60 causes a limited amount of rotation of the contactor 64, due to the sliding engagement between the contactor and the contact points 41 and 42. When the contactor 64 ismoved clockwise, the cam surface141 acts upon the stem 128 and causes tilting orrocking movement of the contactor. Such rocking movement is also caused by the sliding engagement between the contactor and the contact points 41 and 42. This combination of sliding, rocking and rotary movement is highly advantageous, because the combined movements insure that good electrical contact will be established and maintained by the contactor with the contact points, even with very small contact pressure. The rotary movement of the contactor brings new portions of the contactor into play with each cycle so that the effects of wear and electric arcing are equalized around the contactor.

When the carriage 60 is swung counterclockwise, the

contactor 64 engages the contact point 43 with a similar combination of sliding, rotary and rocking movements. The cam surface 142 engages and tilts the stem 128 of the contactor.

The contactor 64 moves very freely over the contact points 41, 42 and 43 so that the operation of the switch is not materially impeded by friction. Thus, the return springs 78 and 80 are readily able to return the switch to. its neutral position even though the strength of the return springs is quite small. The centering action of the return springs is supplemented by the centering action between the contactor 64 and the central contact point 41, as previously described.

Preferably, the contactor 64 is made of a material which will withstand electric arcing and which will not become stuck or welded to the contact points 42 and 43 due to electric arcing. As already indicated, the contact points 42 and 43 are preferably made of a silver contact alloy so as to provide good electrical contact with light contact pressure. The contactor 64 is preferably made of a copper-cadmium alloy, which is highly resistant to welding to the silver contacts 42 and 43. By Way of example, a suitable alloy may consist of about 1% cadmium and 99% copper. The central contact point 41 may be made of some copper-cadmium alloy. By way of further example, a suitable silver contact alloy may consist of about 75% silver, 24 /z% copper and /2% nickel.

As shown in FIGS. 1 and 2, an isolated terminal lug 146 is mounted on the insulating base plate 40 of the switch. The terminal lug 146 may be employed in wiring the switch into the motor circuit. Thus, two or more wires may be soldered to the terminal lug 146.

FIGS. 58 illustrate a modified carry-over switch 10a which is intended for use with a unidirectional electric motor, rather than reversible motor, as in the case of the switch 10. The switch 10a is similar to the switch 10, except that the contact joint 42 is omitted, leaving only the contact points 41 and 43. The insulating base plate 40 is formed with only a single notch or recess 148 which affords clearance for the carriage 60 to swing in a counterclockwise direction, as shown in FIG. 5. In the doublethrow switch of FIGS. 1-4, two such notches 148 are formed in the base plate 40 to afford clearance for both clockwise and counterclockwise movement.

FIG. 10 illustrates a modified circuit for use with the unidirectional switch 10a of FIGS. 58. The circuit employs a unidirectional motor ing switch 118a is employed, having only the contactor 121 and one contact 123, the other contact 122 being omitted.

It may be helpful to review the operation of the carryover switch in terms of the modified unidirectional switch 10a of FIGS. 5-8 and 10. When it is desired to index the television tuner 12 to another channel setting, the switch 118a is closed to start the motor 16a. The operation of the motor 16a causes the drive disc 28 to rotate clockwise. Accordingly, the shoulder 72 at the end of the notch 70 engages the triangular operating arm 66 and causes the arm 66 and the carriage 60 to swing in a counterclockwise direction. In this way, the contactor 64 is moved into bridging relation between the contact points 41 and 43. The circuit thus established by the contactor 64 duplicates the circuit initially established by the switch 118a so that the motor 16a will continue to run when the switch 118a is released.

The clockwise rotation of the disc 28 causes the pin 30 to index the star wheel 32 through one step so that the next adjustable cam lobe 76 comes opposite the cam follower 82. If such cam lo'be 76 is inactively positioned, it does not exert pressure on the cam follower 82, with the result that the return spring 80 causes the cam follower to rock upwardly in a counterclockwise direction, opposite to the direction shown in FIG. 2. When the notch 70 in the disc 28 comes opposite the triangular 16a having only the leads 111 and 113, the lead 112 being omitted. A modified start operating arm 66, the switch carriage 60 remains in its operated position, due to the lack of a return spring action. Thus, the motor continues to operate so that the drive disc 28 is rotated through at least one more revolution.

When an actively positioned cam lobe 76 comes opposite the cam follower 82, it pushes the cam follower downwardly, to the position shown in FIG. 1, so that the return spring 80 is flexed. When the notch 70 comes opposite the arm 66, the return spring 80 is able to return the switch carriage 60 to its neutral position. Thus, the contactor 64 moves out of engagement with the contact point 43, so that the motor 16a is stopped.

When the carriage 60 is in its neutral or central position, the frusto-conical central contact point 41 engages the frusto-conical slope 138a of the ridge 138 so as to center and locate the contactor 64. This engagement between the contactor 64 and the contact point 41 also has a centering effect upon the carriage 60. Both of the slanting cam surf-aces 141 and 142 on the carriage 60 engage the stem 128 of the contactor 64 so as to center the stem and maintain it in a level position.

When the carriage 60 is swung counterclockwise, the curved ridge 138 engages and slides onto the curved contact point 43 so that a good electrical contact is established and maintained. The cam surface 142 causes the stem 128 to tilt or rock. During each movement of the carriage 60, the contactor 64 rotates slightly due to the sliding or wiping movement between the contactor and the contact points 41 and 43. The combination of sliding, rotary and rocking movements insures the maintenance of good electrical contact, even with light contact pressure. The rotation of the contactor distributes the wear on the contactor around the annular ridge 138.

It has been found that the carry-over switches of the present invention will remain dependable in operation for an extremely long service life. Life tests have demonstrated that the switches will continue to operate on a dependable basis even after being subjected to a fantastic number of operating cycles, amounting literally to hundreds of millions of cycles. The extremely long and dependable life of the switch is due to all of the various factors in the construction of the switch, particularly the construction and arrangement of the contact points, the contactor, the insulating base plate and the carriage.

Various other modifications, alternative constructions and equivalents may be employed without departing from the true spirit and scope of the invention, as exemplified in the foregoing description and defined in the following claims.

We claim:

1. In an electrical switch,

the combination comprising an insulating plate,

a. plurality of contact points mounted on said plate,

a movable carriage made of insulating material,

' means mounting said carriage for swinging movement adjacent said plate,

said carriage having a central disposed actuating arm and a pair of return arms based at angular intervals 7 at opposite sides of the actuating arm,

a disc-shaped contactor mounted on said carriage and movable therewith into bridging relation to said contact points,

said carriage having a bore therein loosely receiving said contactor,

said contactor having a stem connected axially thereto,

said carriage having an opening communicating with said bore and loosely receiving said stem,

a coil spring received around said stem and compressed between'saidcarriage and said contactor for biasing said contactor toward said contact points,

said contactor having an annular ridge of curved cross section thereon for engaging said contact points,

1 and a pair of slanting cam surfaces formed on said carriage along the edges of said opening and engage'able with said stem for tilting said contactor to facilitate the movement of said contactor over said conta points.

2. In an electrical switch,

the combination comprising a plurality of conta points,

a supporting member for supporting said contact points,

a movable carriage,

means mounting said carriage for swinging movement adjacent said supporting member,

a disc-shaped contactor mounted on said carriage for movement therewith into bridging relation to said contact points,

biasing means for biasing said contactor toward said contact points,

and an annular ridge of curved cross section formed on said contactor and slidably engageable with said contact points.

3. The combination of claim 2,

including means on said carriage for rotatably supporting said contactor to present new portions of said annular ridge to said contact points wtih repeated operations of said movable carriage.

4. The combination of claim 2,

in which one of said contact points is generally frustoconical,

said ridge having a generally frusto-conical inner slope for engagement wtih said frusto-conical contact point.

5. The combination of claim 2,

in which at least one of said contact points is made of a silver alloy,

and in which said contactor is made of a copper-cadmium alloy.

6. In an electrical switch,

the combination comprising a plurality of contact points,

a supporting member for supporting said contact points,

a movable carriage,

means mounting said carriage for swinging movement adjacent said supporting member,

a disc-shaped contactor mounted on said carriage for movement therewith into bridging relation to said contact points,

biasing means for biasing said contactor toward said contact points,

a stern connected axially to said contactor,

and at least one slanting cam surface on said carriage for engaging said stem and tilting said contactor to facilitate movement of said contactor over said contact points.

7. The combination of claim 6,

in which said carriage is formed with an opening receiving said stem,

and in which said cam surface is formed along an edge portion of said opening.

8. The combination of claim 6,

in which said contactor is formed with an annular ridge of curved cross section for engaging said contact points.

9. The combination of claim 8,

in which one of said contact points is generally frustoconical,

said ridge having a generally frustc-conical inner slope for engagement with said frusto-conical contact point.

p 10. In an electrical switch,

the combination comprising a plurality of contact points,

a supporting member for supporting said contact points,

a movable carriage,

means mounting said carriage for swinging movement adjacent said supporting member,

a disc-shaped contactor mounted on said carriage for movement therewith into bridging relation to said contact points,

biasing means for biasing said contactor toward said contact points,

a stem connected axially to said contactor,

and a pair of oppositely slanting cam surfaces on said carriage and engageable with said stem for tilting said 'contactor in accordance with the movement of said carriage.

ll. The combination of claim 10,

in which said carriage is formed with an opening for receiving said stem,

said cam surfaces being formed along portions of the edge of said opening.

12. The combination of claim 10,

in which said contactor is formed with an annular ridge of curved cross sections for engaging said contact points.

13. The combination of claim 12,

in which one of said contact points is generally frustoconical,

said ridge having a generally frusto-conical inner slope for engagement with said frusto-conical contact point.

14. The combination of claim 13,

in which at least one of said contact points is generally dome-shaped for engaging said annular ridge.

15. In an electrical switch,

the combination comprising a plurality of contact points,

a supporting member for supporting said contact points,

a movable carriage,

means mounting said carriage for swinging movement adjacent said supporting member,

a disc-shaped container mounted on said carriage for movement therewith into bridging relation to said contact points,

biasing means for biasing said contactor toward said contact points,

a stem connected axially to said contactor,

and a pair of slanting cam surfaces on said carriage for engaging said stem and tending to center said stern between said cam surfaces.

References Cited UNITED STATES PATENTS 3,261,931 7/1966 Golbcck et a1. 200-11 ROBERT K. SCHAEFER, Primary Examiner.

J. R. SCOTT, Assistant Examiner. 

2. IN AN ELECTRICAL SWITCH, THE COMBINATION COMPRISING A PLURALITY OF CONTACT POINTS, A SUPPORTING MEMBER FOR SUPPORTING SAID CONTACT POINTS, A MOVABLE CARRIAGE, MEANS MOUNTING SAID CARRIAGE FOR SWINGING MOVEMENT ADJACENT SAID SUPPORTING MEMBER, A DISC-SHAPED CONTACTOR MOUNTED ON SAID CARRIAGE FOR MOVEMENT THEREWITH INTO BRIDGING RELATION TO SAID CONTACT POINTS, BIASING MEANS FOR BIASING SAID CONTACTOR TOWARD SAID CONTACT POINTS, AND AN ANNULAR RIDGE OF CURVED CROSS SECTION FORMED ON SAID CONTACTOR AND SLIDABLY ENGAGEABLE WITH SAID CONTACT POINTS. 